JPS5858372B2 - Method for producing foamable self-extinguishing thermoplastic resin particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing foamable self-extinguishing thermoplastic resin particles.

More specifically, when the foamable self-extinguishing thermoplastic resin particles obtained by the method of the present invention are heated using a heating medium such as steam, primary foamed particles with a low specific gravity can be obtained;
When these primary foamed particles are molded in a mold, each primary foamed particle has good fusion properties, and a foamed molded article of any shape can be obtained. The present invention aims to provide expandable flame-retardant thermoplastic particles that can be endowed with self-extinguishing properties and heat resistance.

Foamed molded bodies made of thermoplastic resins are used as insulation materials in cold storage warehouses and as heat insulating materials in greenhouses, and it is especially possible to obtain any foamed molded body made from expandable thermoplastic resin particles. Because of this, it is widely used in containers for food transportation, flooring materials in buildings, and heat/cold insulation materials for tanks.

However, foamed molded bodies made of thermoplastic resin are more easily combustible than non-foamed molded bodies, so it is desired that the foamed molded bodies have self-extinguishing properties.

For this reason, research is being widely conducted to obtain self-extinguishing foam molded articles by adding flame retardants to thermoplastic resins.

In order to obtain a foam molded article having an arbitrary shape, it is necessary to add a flame retardant and a foaming agent to a particulate thermoplastic resin to form foamable self-extinguishing thermoplastic resin particles.

BACKGROUND ART Foamable self-extinguishing polystyrene resin particles are known as a raw material for obtaining a foamed molded article having a low specific gravity and an arbitrary shape.

A foamed molded product obtained by foam molding using self-extinguishing polystyrene resin particles that can be easily expanded is self-extinguishing,
While it is possible to obtain any shape, it has good heat resistance, chemical resistance,
It had drawbacks such as poor oil resistance.

For this reason, it has been impossible to use it as a heat or cold insulation material for pipes that require heat resistance, chemical resistance, and oil resistance.

On the other hand, foamed molded products made of polypropylene resin are known as self-extinguishing products and have excellent heat resistance, chemical resistance, oil resistance, and the like.

Since the foam is obtained using an extruder, it is limited to sheet, plate, or rod shapes.

In order to obtain an arbitrary shape, a sheet-like or plate-like foam molded product is placed in a mold having a cavity of the desired shape in advance using means such as pressing.

If such a method is used, it is limited to merely producing a wavy-like uneven pattern on the surface, and the processing cost is high, so it is not an excellent method from an industrial point of view.

Therefore, attempts have been made to add a blowing agent to polypropylene resin particles.

However, in order to obtain a foam molded product with a low specific gravity, it is necessary to contain a hydrocarbon foaming agent that is gaseous or liquid at room temperature, such as butane, pentane, or dichlorofluoromethane, in the polypropylene resin particles. However, since polypropylene resin has high gas permeability, the foaming agent contained in the resin particles quickly evaporates, making it impossible to obtain a foamed molded product with a low specific gravity.

Furthermore, since a large amount of flame retardant is required to make polypropylene resin self-extinguishing, there is a drawback that the fusion properties during foam molding are deteriorated due to this.

In view of the above points, the inventor of the present invention conducted extensive research and found that polypropylene resin particles were used as cores, the cores were pre-contained with antimony trioxide, and the cores were impregnated with styrene monomer to which a polymerization catalyst was added. By adding a flame retardant and a foaming agent to the thermoplastic resin particles obtained by polymerizing the styrene monomer in a thermoplastic resin, it is possible to form any desired foamed molded product with heat resistance, chemical resistance, oil resistance, and low specific gravity. The present invention was completed based on the finding that foamable self-extinguishing thermoplastic resin particles can be obtained that can be used as a raw material for obtaining foamable, self-extinguishing thermoplastic resin particles.

That is, in the present invention, 25 to 45 parts by weight of polypropylene resin particles containing 2.5 to 10 parts by weight of antimony trioxide are suspended in an aqueous suspension, and 75 to 55 parts by weight of vinyl fragrance are suspended in the suspension. A group monomer and a flame retardant are added and polymerized in the presence of a polymerization catalyst to form graft-polymerized thermoplastic resin particles. A method for producing foamable self-extinguishing thermoplastic resin particles, characterized by impregnating them with a blowing agent, and an aqueous suspension of 25 to 45 parts by weight of polypropylene resin particles containing 2.5 to 10 parts by weight of antimony trioxide. 75 to 55 parts by weight of a vinyl aromatic monomer is added to the suspension and polymerized in the presence of a polymerization catalyst to form graft-polymerized thermoplastic resin particles. The gist of the present invention is a method for producing foamable self-extinguishing thermoplastic resin particles, which comprises impregnating a blowing agent consisting of a fuel agent and a gaseous or liquid hydrocarbon or halogenated hydrocarbon at room temperature.

In the method of the present invention, the polypropylene resin contains, in addition to polypropylene homopolymer, block copolymers and random copolymers of polypropylene containing 50 weight φ or more of polypropylene and other polyolefins, or 50 weight φ or more of polypropylene. It means a mixed polymer of polypropylene and other polyolefins.

In addition, other polyolefins used in the method of the present invention include polyethylene, ethylene-vinyl acetate copolymer, ethylene-vinyl chloride copolymer, ethylene-propylene rubber,
Examples include polyisobutylene, butyl rubber, styrene-butadiene rubber, polybutene, polybutadiene, etc., and one or more of these may be used as a mixture.

In the method of the present invention, the foamable self-extinguishing thermoplastic resin particles obtained by the method of the present invention have a foaming agent retention property, the self-extinguishing thermoplastic resin particles foamed to a low specific gravity, and the self-extinguishing thermoplastic resin foam molding. In order to increase the impact strength of the body at low temperatures, a polypropylene resin obtained by random copolymerization of propylene and ethylene containing 1 to 10% polyethylene by weight is preferably used.

In order to quickly absorb the vinyl aromatic monomer added in the method of the present invention, the polypropylene resin is used in particulate form.

The size of the particles is preferably spherical, flat or pellet-like with a diameter between 0.5 and 10.

In the method of the present invention, antimony trioxide is contained in the polypropylene resin particles in advance.

In order to make polypropylene resin particles contain antimony trioxide, for example, antimony trioxide is added to polypropylene resin in the form of powder or particles, mixed, and then supplied to an extruder and heated and melted and kneaded. It can be obtained by extruding into a large number of thin bodies through a mold having a large number of slits attached to the tip, and cutting the thin bodies with a pelletizer.

Antimony trioxide contained in the polypropylene resin particles acts as a flame retardant aid.

That is, in order to make the polypropylene resin self-extinguishing, it is necessary to incorporate a large amount of flame retardant into the polypropylene resin, but the presence of monohyantimony triate can reduce the amount of flame retardant used. .

Accordingly, the amount of antimony trioxide contained in the polypropylene resin in the method of the present invention is 2.5 to 10 weight φ based on the polypropylene resin.

A content of less than 2.5 weight φ is not preferable because it causes variations in self-extinguishing properties and increases the amount of flame retardant used.

On the other hand, if the weight is more than 10%, the effect such as cracking cannot be improved, and the fusion properties of the obtained foamed molded product are deteriorated, which is not preferable.

Vinyl aromatic monomers used in the method of the present invention include styrene, α-methylstyrene, ethylstyrene, chlorostyrene, bromostyrene, vinyltoluene,
A monomer such as vinyl xylene, isopropyl xylene, etc. alone or a mixture of two or more thereof, and which can be copolymerized with a vinyl aromatic monomer containing 50% of these vinyl aromatic monomers (e.g., acryloni) It may also be a mixture with IJ, methyl methacrylate, methyl acrylate, etc.

Polymerization catalysts used in the method of the present invention include organic peroxides such as benzoyl peroxide, tert-butyl perbenzoate, lauroyl peroxide, tert-butyl peroxy-2-ethylhexanate, and tert-butyl peroxide; Azo compounds such as butyronitrile and azobisdimethylvaleronitrile are used.

These polymerization catalysts may be used alone or in combination of two or more.

The polymerization catalyst can be used by being dissolved in the above-mentioned vinyl aromatic monomer, or it can also be used by being dissolved in a solvent such as benzene, toluene, or xylene that does not inhibit polymerization.

In the method of the present invention, a flame retardant is used to impart self-extinguishing properties to the polypropylene resin particles.

Such flame retardants include tribromophenol allyl ether, tetrabromophenol allyl ether, pentafluoromophenol allyl ether, tetrabromobisphenol A bisallyl ether, tetrabromobisphenol A bis2,3-dibromopropyl ether, triflomophenyl cyfuro. Examples include pyl ether, hexabromocyclototicane, hexabromobenzene, pentabromophenol, pentabromotoluene, pentabromochlorodiphenyl ether, tris(2,3-dibromopropyl) phosphate, and the like.

The flame retardants used in the method of the present invention may be used alone or in combination of two or more.

In particular, among the above flame retardants, those having a melting point of 90°C or higher are tetrabromobisphenol A allyl ether, hexabromocyclododecane, and tetrabromobisphenol A bis2.
, 3-dibromopropyl ether is preferably used.

The reason why a flame retardant with a melting point of 90°C or higher is preferable is that when a flame retardant is added to polypropylene resin particles, the heat resistance of the resulting foam molded product decreases due to the internal plasticizing effect of the flame retardant. This is because in order to minimize the decrease as much as possible, a material that melts at a higher temperature is required.

The flame retardant has polypropylene resin particles as a core, and is formed into thermoplastic resin particles at the same time as the core is impregnated with a vinyl aromatic monomer, or during polymerization when the core monomer is polymerized, or when the polymerization of the monomer is completed. added later.

Furthermore, it can also be used by dividing it into each process.

When adding a flame retardant in such a process, the flame retardant is dissolved in a vinyl aromatic monomer, a solvent such as benzene or toluene, or a blowing agent, and then added to the polypropylene resin particles or thermoplastic resin particles.

When a flame retardant is added during polymerization, it is preferable to dissolve it in the vinyl aromatic monomer and disperse it in an aqueous suspension after the polymerization is completed.

In addition to flame retardants, t-butylcumyl peroxide, dicumyl peroxide, α,α-bis(t-butylperoxy)P-diisopropylbenzene, 2,5-dimethyl 2,5-di(t-butylperoxide), oxy)hexyne
Flame retardant aids made of organic peroxides such as 3,2,5-dimethyl-2,5-dibenzoylperoxyhexane and t-butylperoxyisopropyl carbonate can also be used singly or in combination of two or more. .

In the method of the present invention, a crosslinking agent is not necessarily required, but may be added.

Examples of crosslinking agents include di-t-butyl peroxide, t-butyl cumyl peroxide, and di-cumyl peroxide.
Peroxide, α,α-bis(t-butylperoxy)/p-di-isopropylbenzene, 2,5-di-methyl-2,5-di(t-butylperoxy)/hexyne 3
．． Examples include 2,5-dimethyl-2°5-di(benzoyl peroxy)hexane and t-butyl peroxy isopropyl carbonate.

Additionally, crosslinking agents are generally used together with crosslinking aids.

As a crosslinking aid, divinylbenzene, polyethylene glycol dimethacrylate, triallyl cyanurate, diacryl phthalate, ■, 3-butadiene, 1゜2
- Functional vinyl compounds such as polybutadiene and 1,4-polybutadiene, quinone dioximes, bisamides and the like can be mentioned.

To specifically explain the method of the present invention, first, antimony trioxide is added to polypropylene resin, mixed thoroughly in a tumbler, and then fed to an extruder.The polypropylene resin is melted in the extruder and antimony trioxide is and knead evenly.

After kneading, the mixture is extruded through a die attached to the tip of the extruder into a number of thin bodies, and the thin bodies are cooled by passing through a water tank.
Cut into particles using a pelletizer or the like.

The polypropylene resin particles containing antimony trioxide thus obtained are suspended in an aqueous suspension to which a dispersant is added.

As this dispersant, for example, polyvinyl alcohol, methyl cellulose, calcium phosphate, magnesium pyrophosphate, calcium carbonate, etc. are used, and these dispersants are generally used by adding 0.01 to 5% by weight to water. .

Then, a vinyl aromatic monomer such as a styrene monomer and a polymerization catalyst are added to the suspension in which the polypropylene resin particles are dispersed.

This addition method may be to add the whole amount at once, or to gradually drop it in small amounts.

The vinyl aromatic monomer and the polymerization catalyst may be added separately, or the polymerization catalyst may be dissolved or mixed in advance with the vinyl aromatic monomer and added.

Further, the polymerization catalyst can also be used by dissolving it in a solvent that does not interfere with the polymerization reaction.

Examples of such solvents include toluene, benzene, 1,2 dichloropropane, and the like.

In the present invention, when a flame retardant is added during polymerization, it is used after being dissolved in the vinyl aromatic monomer to which the polymerization catalyst is added.

In the method of the present invention, when a crosslinking agent is used as necessary, the crosslinking agent may be used by being dissolved in the vinyl aromatic monomer, or may be used by being dissolved in the solvent for the polymerization catalyst.

When using a relatively large amount of vinyl aromatic monomer, it is desirable to gradually add the vinyl aromatic monomer to the suspension in small amounts to prevent the formation of homopolymers of the vinyl aromatic monomer. .

The vinyl aromatic monomer dropped into the suspension permeates into the interior of the polypropylene resin particles and is polymerized or polymerized and crosslinked in the polypropylene resin particles.

Graft polymerization also occurs simultaneously through such a reaction.

In this reaction, 25 to 45 parts by weight of the antimony trioxide-containing polypropylene resin particles and 75 to 55 parts by weight of a vinyl aromatic monomer are used, but if the monomer is less than 55 parts by weight, the resultant foam is It is not possible to obtain a foam molded product with excellent rigidity, shape retention, and self-extinguishing properties, and conversely, if the vinyl aromatic monomer is 75 parts by weight or more, the resulting foam molding has poor heat resistance, oil resistance, etc. properties are reduced.

In the method of the present invention, the mixing ratio of polypropylene resin particles containing antimony trioxide and vinyl aromatic monomer is
By using 25 to 45 parts by weight of the particles and 75 to 55 parts by weight of the monomer, primary foamed particles with a low specific gravity can be obtained when the resulting foamable self-extinguishing thermoplastic resin particles are primarily foamed. Furthermore, when these foamed particles are molded in a mold, they have good fusion properties and a foamed molded product of any shape can be obtained, and the molded foamed molded product has self-extinguishing properties, heat resistance, It has excellent chemical resistance and oil resistance, as well as rigidity and shape retention.

The vinyl aromatic monomer dropped into the suspension is quickly absorbed into the inside of the polypropylene resin particles, and polymerization or polymerization/crosslinking reaction is performed in the polypropylene resin particles, thereby obtaining the thermoplastic resin particles of the present invention. It will be done.

The components of the obtained thermoplastic resin particles are a polypropylene resin, a vinyl aromatic resin, and a propylene-vinyl aromatic graft resin.

Because the propylene-vinyl aromatic resin is contained in the thermoplastic resin particles due to the above reaction, the polypropylene resin does not undergo phase separation from each other as seen when polypropylene resin and vinyl aromatic resin are mixed. It can exhibit the effect of a binder to improve the compatibility between the resin and the vinyl aromatic resin.

Accordingly, at least 2 ml of propylene-vinyl aromatic graft resin is required to be contained in the thermoplastic resin particles.

If the amount is less than 2, the binder effect for improving compatibility will not be sufficient and some phase separation will occur, which is not preferable.

The graft-polymerized and cross-linked particles in the thermoplastic resin particles obtained by the method of the present invention precipitate as an insoluble component (gel component) when heated and dissolved in toluene, xylene, etc.

Further, the graft reaction product of the vinyl aromatic monomer to the polypropylene resin is prepared by the weight increase relative to propylene from the extrusion residue amount of the boiling acetone-benzene (ratio 1:1) mixture.

The presence of the gel component or the graft reactant can improve the foaming agent retention of the obtained thermoplastic resin particles and the fusion moldability during foam molding.

In the method of the present invention, thermoplastic resin particles obtained by polymerizing the polypropylene resin particles with a vinyl aromatic monomer are impregnated with a blowing agent under pressure in an aqueous suspension.

The suspending agent used in the aqueous suspension is one added to prevent the thermoplastic resin particles from binding or coalescing with each other during impregnation with the blowing agent, such as partially saponified polyvinyl alcohol, In addition to organic compounds such as polyacrylates, polyvinylpyrrolidone, carboxymethylcellulose, methylcellulose, calcium stearate, and ethylene bisstearamide, calcium pyrophosphate, calcium phosphate, calcium carbonate, magnesium carbonate,
Examples include inorganic compounds consisting of fine powder hardly soluble in water, such as magnesium phosphate, magnesium pyrophosphate, and magnesium oxide.

In the method of the present invention, when an inorganic compound is used as a suspending agent, it is preferable to use a surfactant such as sodium dodecylbenzenesulfonate.

In addition, the blowing agents used in the method of the present invention include easily volatile blowing agents, that is, aliphatic hydrocarbons such as propane, n-butane, 1so-butane, n-pentane, 1so-pentane, and n-hexane; Examples include cycloaliphatic hydrocarbons such as cyclopenkune and cyclohexane, and halogenated hydrocarbons such as methyl chloride, ethyl chloride, dichlorodifluoromethane, chlorodifluoromethane, and trichlorofluoromethane.

These blowing agents are generally used in a ratio of 3 to 40 parts by weight based on the thermoplastic resin particles.

Also, add an organic solvent such as toluene or xylene in an amount of φ (1-5
weight%) may be used in combination.

Impregnation of a blowing agent or a blowing agent and a flame retardant can be carried out by, for example, suspending thermoplastic resin particles in a suspension containing a suspending agent in an autoclave, and heating the suspension to impregnate the blowing agent or a blowing agent and a flame retardant. Impregnated by press-fitting, foamable self-extinguishing thermoplastic particles are obtained.

In the method of the present invention, stabilizers for improving the thermal stability of the polypropylene resin include 2,6 ditertiarybutylmethylphenol, 2,4-dimethyl-6-cuchabutylphenol, tris(2-methyl-4- Hydroxy-5-tashabutylphenyl)butane, dilaurylthiodipropionate, distearylthiodipropionate, stearyllaurylthiodipropionate, etc. can be added singly or in combination of two or more.

The stabilizer is 0.0% for the polypropylene resin particles.
It is preferable to use 5 to 65 to 6 parts by weight.

If the amount is less than 0.05 parts by weight, the stability effect will be poor, and if it exceeds 6 parts by weight, the self-extinguishing property will be poor.

In order to improve the kneading of the polypropylene resin and antimony dioxide, a stretched material such as polybutene can also be used.

The spreading agent is 0.1 to 0.1 to polypropylene resin.
3. O is used within the range of parts by weight.

Other colorants, antistatic agents, etc. can be used as appropriate.

The foamable self-extinguishing thermoplastic resin particles obtained by the method of the present invention are inexpensive because the amount of flame retardant used is small compared to conventional methods, and when the particles are heated, they undergo primary foaming with a low specific gravity. When the particles are obtained and the primary foamed particles are molded in a mold for molding, the respective primary foamed particles have good fusion properties and a foamed molded article of an arbitrary shape is obtained, and the obtained foamed The molded product has excellent properties such as self-extinguishing property, heat resistance, chemical resistance, and oil resistance, and is also excellent in terms of rigidity and shape retention. It can be provided as a raw material for

Examples of the present invention will be shown below.

In the examples, all parts and weights are by weight unless otherwise specified.

Example 1 100 parts by weight of polypropylene (a random copolymer containing 3% polyethylene), 0.3 parts by weight of polybutene, and 5 parts by weight of antimony trioxide were blended in a tumbler,
The mixture was kneaded in an extruder equipped with a mold having a large number of 1.07 ftm slits to obtain pellet-shaped polypropylene resin particles having strands with an average diameter of 1.0 mm and an average length of 1.0 mounds.

30 parts by weight of the polypropylene resin particles obtained above, 10 parts by weight of water
0 parts by weight, sodium dodecylbenzenesulfonate 0.0
Put 2 parts by weight and 0.3 parts by weight of metathetical magnesium pyrophosphate into an autoclave equipped with a stirrer, and while maintaining the temperature at 90°C, add 0.25 parts by weight and 0.05 parts by weight of benzoyl peroxide and t-butyl perbenzoate, respectively. 70 parts by weight of dissolved styrene monomer was added dropwise over a period of 6 hours, and after being held for an additional hour, the temperature was raised to 140°C.

After polymerizing for another 2 hours while maintaining this temperature, 8
Cool to 0°C to obtain thermoplastic resin particles, and add 1 part by weight of toluene, 2 parts of tetrabromobisphenol A bimata,
5 parts by weight of 3-dibromopropyl ether and 1 part by weight of tetrabromobisphenol allyl ether were added, and after sealing, 18 parts by weight of butane was injected.

After raising the temperature of this system to 100°C and maintaining it for an additional 6 hours,
After cooling to 30'C, foamable self-extinguishing thermoplastic resin particles were taken out.

After storing these particles in a sealed container at a temperature of 15°C for 4 days, they were foamed under pressure with water vapor at 3.5 kg/cyyt (gauge pressure), and the particles that had been primarily foamed to a bulk specific gravity of 0.030 were After storing it at room temperature, it is filled into the mold and 4.2
When pressure molded with steam at kg/= (gauge pressure),
A foam molded article having a specific gravity of 0.030 was obtained.

Note that the grafting rate of the thermoplastic resin particles before adding the flame retardant and the blowing agent was 5.2%.

The self-extinguishing property of the foam molded product obtained above was evaluated using the JISA9511 combustion test method.
．． It was a self-extinguishing thermoplastic resin foam molded product that self-extinguished in 0 seconds and 1.7 seconds on average and passed the JIS standard.

In addition, the heat resistant dimensional change rate is -1.8φ (The method for measuring the heat resistant dimensional change rate is to cut a foamed molded product into a sample piece with a length of 250 mm and a width of 50 mm. Place pins at 200 mm intervals in the center of the sample piece, and use a caliper to measure the original size ( After measuring lo), it was left in a hot air circulation constant temperature bath set at 90°C ± 1°C for one week.

After that, the sample was taken out and left at room temperature for 2 hours, and the pin spacing dimension (1) was measured again in the same manner to determine the dimensional change rate using the following formula.

lo-1 Dimensional change rate = -X100 (many) i.

The following examples will also be expressed in the same manner.

)Met.

The degree of fusion of the above-mentioned foam molded product is so% (the degree of fusion is 100% when the surface of the foamed particles does not appear at all on the fractured surface when the foamed molded product is broken by hand, and 100% when the fractured surface is entirely the surface of the foamed particles. The ratio of the surface of the foamed particles in the fractured surface is expressed as a percentage, with the case where the ratio is 0%.

The following examples are also expressed in the same manner.

)Met. Examples 2 to 6 Foamed molded products were obtained and evaluated in the same manner as in Example 1 except that the type and amount of flame retardant were changed.

The same applies to the following examples.

Examples 7 to 14 Foam molded products were obtained and evaluated in the same manner as in Example 1, except that the amount of antimony trioxide blended into the polypropylene resin and the type and amount of the flame retardant were changed.

Examples 15 to 19 In Example 1, 10 parts by weight of antimony trioxide is kneaded into the polypropylene resin, the ratio of the polypropylene resin particles obtained by an extruder and the styrene monomer to be dropped is changed, and further added after the polymerization is completed. A foam molded article was obtained in the same manner except that the type and amount of the flame retardant agent were changed.

The foamed molded product obtained here was evaluated in the same manner as in Example 1.

Example 20 30 parts by weight of polypropylene resin particles kneaded with antimony trioxide obtained in Example 1, 100 parts by weight of water, 0.02 parts by weight of sodium dodecylbenzenesulfonate, 0.3 parts by weight of metathesized magnesium pyrophosphate. 0.35% each of benzoyl peroxide, t-butyl perbenzoate, and tetrabromobisphenol A1 bisallyl ether were placed in an autoclave equipped with a stirrer, and while maintaining the temperature at 90°C.
．． Styrene monomer 70 dissolved in 0.06°15 parts by weight
Parts by weight were added dropwise over a period of 7 hours, and after holding for an additional 2 hours, the temperature was raised to 140'C.

After being maintained at this temperature for 3 hours, it was cooled to 80°C, and a mixture of 0.1 part by weight of butylated hydroxytoluene, 0.2 parts by weight of thiopropionate laurate dissolved in 1.0 parts by weight of toluene, and tetrabisphenok were prepared. 6 parts by weight of Abis 2,3-dibromopropyl ether were added, and 18 parts by weight of butane were then pressurized.

After raising the temperature of this suspension to 100'C and holding it for 6 hours,
After cooling to 30'C, foamable self-extinguishing thermoplastic resin particles were taken out.

According to Example 1, the self-extinguishing foamed molded article with an average self-extinguishing time of 1.7 seconds exhibited a heat resistant dimensional change rate of -2.5% and a degree of fusion of 90%.

Comparative example Polystyrene 100 with a diameter distribution of 1.0 to 1.4 degrees
Parts by weight, 100 parts by weight of pure water, 0.02 parts by weight of sodium dodecylbenzenesulfonate, and 0.3 parts by weight of metathetical magnesium pyrophosphate were placed in an autoclave equipped with a stirrer, and while stirring, 5 parts by weight of toluene Q and a flame retardant were added. After adding the specified amount, press-fit 10 parts of butane and 3 parts of pentane.
The temperature was raised to 0°C.

After being held at 100° C. for 6 hours, it was cooled to 30° C., taken out, dehydrated, and dried to obtain expandable polystyrene resin particles.

After storing these particles in a sealed tube for 4 days in a constant temperature room at 15°C,
In an open state, primary foamed particles with a bulk specific gravity of 0.030 were obtained using water vapor at 0.5 ky/i (gauge pressure), and the particles were stored indoors for 24 hours and filled into a layer and a mold.1. It was molded with O1y/i steam.

The obtained foamed molded product was evaluated for self-extinguishing heat resistance and dimensional stability according to Example 1.

Claims (1)

[Scope of Claims] 1. 25 to 45 parts by weight of polypropylene resin particles containing 2.5 to 10 parts by weight of antimony trioxide are suspended in an aqueous suspension, and 75 to 55 parts by weight of polypropylene resin particles containing 2.5 to 10 parts by weight of antimony trioxide are suspended in an aqueous suspension. A vinyl aromatic monomer and a flame retardant are added and polymerized in the presence of a polymerization catalyst to form graft-polymerized thermoplastic resin particles.
1. A method for producing foamable self-extinguishing thermoplastic resin particles, which comprises impregnating them with a blowing agent consisting of 1% halogenated hydrocarbon. 2. The method for producing foamable self-extinguishing thermoplastic resin particles according to claim 1, wherein the polypropylene resin is a random copolymer of propylene and ethylene containing 1 to 10% more polyethylene by weight. 3 The vinyl aromatic monomer is a monomer of styrene, α-methylstyrene, ethylstyrene, chlorostyrene, bromostyrene, vinyltoluene, vinylxylene, isopropylxylene, a mixture thereof, or a mixture of these vinylaromatic monomers. 2. The method for producing foamable self-extinguishing thermoplastic resin particles according to claim 1, which is a mixture of a vinyl aromatic monomer containing a heavy weight upstream and a copolymerizable monomer. 4. The foamable flame retardant according to claim 1, wherein the flame retardant is tetrabromobisphenol A allyl ether, hexabromocyclododecane, or tetrabromobisphenol A bis2,3-dibromopropyl ether having a melting point of 90'C or higher. Method for producing self-extinguishing thermoplastic resin particles. 5. 25 to 45 parts by weight of polypropylene resin particles containing 2.5 to 10 parts by weight of antimony trioxide are suspended in an aqueous suspension, and 75 to 55 parts by weight of a vinyl aromatic monomer are added to the suspension. The particles are polymerized in the presence of a polymerization catalyst to obtain graft-polymerized thermoplastic resin particles, and the particles (
A method for producing foamable self-extinguishing thermoplastic resin particles, which comprises impregnating the flame retardant with a blowing agent consisting of a gaseous or liquid hydrocarbon or halogenated hydrocarbon at room temperature. 6. The method for producing foamable self-extinguishing thermoplastic resin particles according to claim 5, wherein the polypropylene resin is a random copolymer of propylene and ethylene containing 1 to 10 weight percent of polyethylene. 7 The vinyl aromatic monomer is styrene, α-methylstyrene, ethylstyrene, chlorostyrene, bromostyrene, vinyltoluene, vinylxylene, isopropylxylene monomer or a mixture thereof, or 50% by weight of these vinyl aromatic monomers. The method for producing foamable self-extinguishing thermoplastic resin particles according to claim 5, which is a mixture of a vinyl aromatic monomer containing φ or more and a copolymerizable monomer. 8. The foamable flame retardant according to claim 5, wherein the flame retardant is tetrabromobisphenol A allyl ether, hexabromocyclododecane, or tetrabromobisphenol A bis2,3-dibromopropyl ether having a melting point of 90'C or higher. Method for producing self-extinguishing thermoplastic resin particles.